Transifex is used by several translations, and personally I am a fan.

We (python transifex team) have documentation on how to set up, this is however made much easier withsample-workflows, create tx key, and change the config to your language. For an example see:repo

Note that you will have to push all of your existing translation using the tx cli to transifex.

If you have any further questions do not hesitate to ask.